Well Sombra is evil... and dark magic isn't dark magic just for its name...

Dark magic is originating from evil meanings so you can say that dark magic is evil. Some is not but most of the meanings of dark magic are somehow bad for the rest of universal system etc.

So that's why dark magic is usually considered as evil magic. And that's why it is not sad, it's just silly how most of people think dark magic is ALL evil. There, I formed your words to be littlebit better.